To fill the application form you can refer below link

JEE Main 2018 Application Form

You can check the eligibility critera below

- You should born on or after October 1, 1993 are eligible to apply for JEE Main 2018. There is relaxation of 5 years for reserved category.

- You must have passed 12th class or qualifying exam in 2016 or 2017. Appearing students can also apply for this exam.

- It is mandatory for candidates to have taken 5 subjects in 12thor qualifying exam

The 5 subjects for B.Tech/ B.E. are:

1-Language, 2-Physics, 3-Mathematics, 4-Any one of (Chemistry, Biology, Biotechnology, Technical Vocational Subject), 5-Any other subject

- To be eligible for NITs/IIITs anf GFTIs you should have 75% marks in your board exam or you should be in top 20 percentile. For SC/ST you should have 65% marks. 

- You can attempt JEE Main 3 times. 

Good Luck!!